linux-kernel - Re: [PATCH V5 0/2] ublk: add io_uring based userspace block driver

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Message-ID: <Ys+p79SG+9QBjo7x@T590>
Date:   Thu, 14 Jul 2022 13:30:23 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        ZiyangZhang <ZiyangZhang@...ux.alibaba.com>,
        Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
        ming.lei@...hat.com
Subject: Re: [PATCH V5 0/2] ublk: add io_uring based userspace block driver

On Wed, Jul 13, 2022 at 08:59:16PM -0600, Jens Axboe wrote:
> On 7/13/22 8:54 PM, Jens Axboe wrote:
> > On 7/13/22 6:19 PM, Ming Lei wrote:
> >> On Wed, Jul 13, 2022 at 02:25:25PM -0600, Jens Axboe wrote:
> >>> On 7/13/22 8:07 AM, Ming Lei wrote:
> >>>> Hello Guys,
> >>>>
> >>>> ublk driver is one kernel driver for implementing generic userspace block
> >>>> device/driver, which delivers io request from ublk block device(/dev/ublkbN) into
> >>>> ublk server[1] which is the userspace part of ublk for communicating
> >>>> with ublk driver and handling specific io logic by its target module.
> >>>
> >>> Ming, is this ready to get merged in an experimental state?
> >>
> >> Hi Jens,
> >>
> >> Yeah, I think so.
> >>
> >> IO path can survive in xfstests(-g auto), and control path works
> >> well in ublksrv builtin hotplug & 'kill -9' daemon test.
> >>
> >> The UAPI data size should be good, but definition may change per
> >> future requirement change, so I think it is ready to go as
> >> experimental.
> > 
> > OK let's give it a go then. I tried it out and it seems to work for me,
> > even if the shutdown-while-busy is something I'd to look into a bit
> > more.
> > 
> > BTW, did notice a typo on the github page:
> > 
> > 2) dependency
> > - liburing with IORING_SETUP_SQE128 support
> > 
> > - linux kernel 5.9(IORING_SETUP_SQE128 support)
> > 
> > that should be 5.19, typo.
> 
> I tried this:
> 
> axboe@...ro-kvm ~/g/ubdsrv (master)> sudo ./ublk add -t loop /dev/nvme0n1
> axboe@...ro-kvm ~/g/ubdsrv (master) [255]> 

That looks one issue in ubdsrv, and '-f /dev/nvme0n1' is needed.

> 
> and got this dump:
> 
> [   34.041647] WARNING: CPU: 3 PID: 60 at block/blk-mq.c:3880 blk_mq_release+0xa4/0xf0
> [   34.043858] Modules linked in:
> [   34.044911] CPU: 3 PID: 60 Comm: kworker/3:1 Not tainted 5.19.0-rc6-00320-g5c37a506da31 #1608
> [   34.047689] Hardware name: linux,dummy-virt (DT)
> [   34.049207] Workqueue: events blkg_free_workfn
> [   34.050731] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   34.053026] pc : blk_mq_release+0xa4/0xf0
> [   34.054360] lr : blk_mq_release+0x44/0xf0
> [   34.055694] sp : ffff80000b16bcb0
> [   34.056804] x29: ffff80000b16bcb0 x28: 0000000000000000 x27: 0000000000000000
> [   34.059135] x26: 0000000000000000 x25: ffff00001fe9bb05 x24: 0000000000000000
> [   34.061454] x23: ffff000005062eb8 x22: ffff000004608998 x21: 0000000000000000
> [   34.063775] x20: ffff000004608a50 x19: ffff000004608950 x18: ffff80000b7b3c88
> [   34.066085] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> [   34.068410] x14: 0000000000000002 x13: 0000000000013638 x12: 0000000000000000
> [   34.070715] x11: ffff80000945b7e8 x10: 0000000000006f2e x9 : 00000000ffffffff
> [   34.073037] x8 : ffff800008fb5000 x7 : ffff80000860cf28 x6 : 0000000000000000
> [   34.075334] x5 : 0000000000000000 x4 : 0000000000000028 x3 : ffff80000b16bc14
> [   34.077650] x2 : ffff0000086d66a8 x1 : ffff0000086d66a8 x0 : ffff0000086d6400
> [   34.079966] Call trace:
> [   34.080789]  blk_mq_release+0xa4/0xf0
> [   34.081811]  blk_release_queue+0x58/0xa0
> [   34.082758]  kobject_put+0x84/0xe0
> [   34.083590]  blk_put_queue+0x10/0x18
> [   34.084468]  blkg_free_workfn+0x58/0x84
> [   34.085511]  process_one_work+0x2ac/0x438
> [   34.086449]  worker_thread+0x1cc/0x264
> [   34.087322]  kthread+0xd0/0xe0
> [   34.088053]  ret_from_fork+0x10/0x20

I guess there should be some validation missed in driver side too, will
look into it.


Thanks,
Ming